The invention relates to a molded case circuit breaker comprising a front panel an orifice arranged in the front panel, a pivoting manual operating handle passing through the orifice and protruding out from said front panel, a surround in the form of a frame protruding out from the front panel and surrounding the orifice, an interchangeable trip unit for automatic opening of the circuit breaker in the event of a fault, and an indicating means, for indicating the trip unit rating.
A state-of-the-art circuit breaker of the kind referred to can be equipped with different trip units, notably with trip units of different ratings, the units being able to be electronic or electromagnetic trip units. The rating or characteristics of the trip unit are inscribed on the front part enabling the fitter or user to check the characteristics of the circuit breaker. Circuit breakers and other electrical devices are generally housed and grouped in electrical cabinets, themselves equipped with a front protection panel, leaving only the operating devices, i.e. the circuit breaker operating handle, accessible. The front protection panel covers the trip unit and the corresponding inscriptions, only removal of the front protection panel enabling the circuit breaker characteristics to be read and checked. It is possible to make an orifice in the front protection panel opposite the inscription, but this operation is complicated and correct positioning of the orifice is not guaranteed. The object of the present invention is to achieve a circuit breaker with an interchangeable trip unit, wherein the characteristics of the trip unit associated with the circuit breaker are visible under all circumstances.